Investigation of compression grating misalignment in ultra-high peak power femtosecond laser systems

The misalignment of the gratings in pulse compressor can introduce residual angular chirp and finally result in a reduction of focused intensity, especially for high peak power femtosecond laser systems with large beam size and broadband spectrum. In this work, we study the angular chirp produced by grating misalignment in different dimensions and comprehensively investigate the various effects on the deterioration of the spatiotemporal characteristics of focused beam. Moreover, two representative ultra-high peak power femtosecond laser systems, featuring with 10 PW peak power/500 mm beam diameter/100 nm spectral width and 50 PW peak power/640 mm beam diameter/200 nm spectral width, are studied. For a drop of effective focused intensity smaller than 10%, the numerical results show that the misalignment of gratings must be kept below ~ 2 μrad and ~ 1 μrad for aforesaid 10 PW and 50 PW lasers, respectively. This work provides meaningful guidelines for the design and construction of the grating compressors in ultra-high peak power femtosecond laser systems.